Engine knock diagnostic suggestions

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jos51700

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So, I swapped the stock 2.0 in my '96 Neon for another stock 2.0. While I had the new engine on the stand replacing the timing belt, I found the stock water pump was severely worn, and my heart sank. It was clearly to the point of losing water. The car I got the motor out of was wrecked and had good compression when I pulled it, so I felt good at the time that the motor was fine, but it's never as good as when you can hear one run.

Forging ahead and fearing the worst, I finally finished the install and...it knocks. It's just one knock, engine speed related, and you can hear it thirty feet away at idle. Car drives fair but seems down on power compared to the second-gen neon I'm driving now, which is a heavier car with identical powertrain.

Any guru's know how to tell a rod knock from piston slap from a dead lifter? I don't know how to tell if it's half-engine-speed or not (i.e. cam vs. crank) but a lifter is easy to check. I looked in all holes with a bore scope prior to install, and all looked fine. I have suspects but would like to get to the bottom of it concretely.

Noise seems to get quieter if I drop it into first and let the car drive the motor.

Thoughts? Suggestions?
 
Kill one cylinder at a time. If it's a rod knock it will get quiet when you take spark away from that cylinder. Piston slap will be worse when the engine is cold and get quieter as it warms up.
 
Kill one cylinder at a time. If it's a rod knock it will get quiet when you take spark away from that cylinder. Piston slap will be worse when the engine is cold and get quieter as it warms up.
Thank you for the tips! I'll give it a shot, but since its coil pack I'll have to be careful not to drop two cylinders at once
 
You can pull one spark plug wire at a time. Or the injector wiring connector.
 
Had loose torque converter/flex plate bolts on a 2.2 Daytona that sounded like a rod knock.
 
Had loose torque converter/flex plate bolts on a 2.2 Daytona that sounded like a rod knock.

I'm positive it's not that, and it sounds 'upper end' to me.

Pulling injector plugs never really made the sound go away, and the car had water pump and engine temp sensor issues, so I'm pretty sure it is piston slap. Anyone want to wager how many miles it'll run that way? I'm tempted to pull the head and oil pan, pull the rods, and just slap in new pistons and rings, but I'm also tempted to just swap in another motor. Again. Ugh.

I did pull the valve cover and didn't find any rockers that weren't pumped up, or anything like that. And I found out how much of a mess it makes to start a Neon with no valve cover. It's funny, this motor is SPOTLESS inside. I've run it over an hour and oil comes out crystal clear. NO sludge or color at all. I had to check and make sure it was oil, which sucks since it knocks.
 
Is it possible that the timing belt jumped a tooth? Might explain down on power and possibly why killing cylinders individually didn't change how things sounded.
 
It's possible but I've done that a couple times on Neons and it never knocked before. I'll check.
 
Anyone want to wager how many miles it'll run that way? I'm tempted to pull the head and oil pan, pull the rods, and just slap in new pistons and rings, but I'm also tempted to just swap in another motor
Put a lot of pistons in those thing back in the day. If the cylinder isn't too bad just stuff one in there. Those thing don't have any piston skirt anyway so they are always noisy.
 
Put a lot of pistons in those thing back in the day. If the cylinder isn't too bad just stuff one in there. Those thing don't have any piston skirt anyway so they are always noisy.

I'm tempted, now. The bore's probably perfect what with low-tension rings and all.
 
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